This invention relates to an information-recording thin film capable of recording frequency modulated analog signals such as images, voices, etc. or digital information such as electronic computer data, facsimile signal, digital audio signal, etc. in real time by a recording beam, such as laser beam, electron beam, etc.
Principles of recording on a thin film by a laser beam are various, and the recording based on changes in atomic configuration such as phase transition (which may be also called "phase change") of film material, photo-darkening, etc. brings about no substantial deformation of the film, and thus has such an advantage that a two-side disk can be obtained by directly bonding two disks. Furthermore, rewriting of recording is possible by properly selecting a composition. Many inventions of such recording have been so far made, and one of the earliest ones is disclosed in U.S. Pat. No. 3,530,441, where many thin films of Te-Ge, As-Te-Ge, Te-O, etc. are mentioned. Japanese Patent Application Kokai (Laid-Open) No. 54-41902 discloses various film compositions such as Ge.sub.20 Tl.sub.5 Sb.sub.5 Se.sub.70, Ge.sub.20 Bi.sub.10 Se.sub.70, etc., and Japanese Patent Application Kokai (Laid-open) No. 57-24039 discloses films of Sb.sub.25 Te.sub.12.5 Se.sub.62.5, Cd.sub.14 Te.sub.14 Se.sub.72, Bi.sub.2 Se.sub.3, Sb.sub.2 Se.sub.3, In.sub.20 Te.sub.20 Se.sub.60, Bi.sub.25 Te.sub.12.5 Se.sub.62.5, CuSe and Te.sub.33 Se.sub.67. However, all of these prior art thin films have disadvantages, when used as once-writable (write-once) or rewritable (reversible) phase transition recording film, such as low crystallization speed, less absorption of semi-conductor laser beam and consequent poor sensitivity, inadequate reproduced signal intensity, poor stability of amorphous state and poor oxidation resistance, and there have been problems in their practical applications.